Mechanical band spread for radio tuning



y 1945' c. F. MATHEWSON 2,400,599

MECHANICAL BAND SPREAD FOR RADIO TUNING Filed June 1, 1944 2 Sheets-Sheet 1 IN VEN TOR. C/Idr/Qs F/Va Z/Ie wson ATTD R N EYS y 21, 1946' C. F. MATHEWSON 2,400,699

MECHANICAL BAND SPREAD FOR RADIO TUNING Filed June 1, 1944 2 Sheets-Sheet 2 w \9 m N o IIIIMQQ m l W a E v w W -';Q

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' C Mir/es F Mathewson ATTORNEYS Patented May 21, 1946 UNITED STATES PATENT OFFICE MECHANICAL BAND SPREAD FOR RADIO TUNING Charles F. Mathewson, Buffalo, N. Y. Application June 1, 1944, Serial No. 538,257

8 Claims.

which embodies a two-speed dial arrangement which will cover the desired ranges and, at the same time, will provide sufficient geared-down vernier drive so that weak signals will not be passed over without hearing them.

A further object of the invention is to provide a mechanical band spreader of an extremely simplified design and construction that will eliminate the diificulties heretofore experienced in the manufacture of previously proposed typ s of such mechanisms, and which will be highly efficient in operation, comparatively inexpensive to make, and capable of bein easily installed to change single speed tuning mechanisms into a two-speed type.

With these and other objects and advantages in view, the invention resides in the certain new and useful combination, construction and arrangement of parts, as will be hereinafter more fullydescribed, set'forth in the appended claims, and illustrated in the accompanying drawings, in which:

Figure 1 is a side elevation of the improved band-spreading mechanism and a tuning condenser mounted on the chassis of a radio receiver, in accordance with the invention;

Figure 2 is a front elevation of the bandspreading mechanism and showing the drive means therefor;

Figure 3 is a vertical section taken on the line 3-3 of Figure 1 Figure 4 is a view identical to that of Figure 3, but showing the relative position of the parts after the drum has been rotated ninety degrees;

Figure 5 is sectional detail of the. key device for switching the mechanism from regular tuning to band-spread tuning;

Figure 6 is an enlarged fragmentary section taken on the line 6-8 of Figure 5; and

Figure 7 is a front view of the dial drum, showing the rocker actuating cam and broachedkeyway for engaging the band-spread mechanism to the condenser shaft through the key.

Referring to the drawings, wherein like characters of reference denote corresponding parts throughout the several views, the embodiment of the invention, as is exemplified therein, is comprised in a shaft I2 having bearing in a frame element ll rising from the chassis B of a radio receiver, at the front side of the tuning condenser A. The shaft l2 has its rearwardly directed end coupled, as at I3, to the rotor shaft of the condenser A, and is afforded added bearing support by collars M and I5 keyed to the same at the front and rear sides of r the frame element II.

Loosely mounted on the shaft I2, immediately in front of the collar I4 is a drum i6, which is -driven by a cable I! having connection with the regular tuning dial (not shown) of the radio receiver. Fixed on the front side of the drum I6 is an eccentric or cam element I8 that is engaged by a yoke 20 at the lower end of a rocker arm or lever !9, which has its upper end pivoted, as at 2|, to a stud 22 projecting forwardly from the frame element H; the stud 22 being provided with a sleeve 23 to space its forward end from the frame element II a proper distance for the support of the rocker arm or lever IS in its cooperative relation with respect to the eccentric or cam element IB.

Fulcrumed at its inner end on the shaft l2, immediately in front of the rocker arm or lever 19, is a second rocker arm or lever 24 and immediately in front of it is yet another or third rocker arm or lever 26, which has its inner end taking the form of a substantially semicircular yoke 21 that is engaged over the shaft [2 and its outer end extending radially outward from the center of the arc defined by the curvature of the yoke 21* and slotted as at 2B, outwardly from the latter for substantially its entire length. The side of the yoke 21, opposite the slotted arm 26, is angularly bent inwardly as at 21', and is pivoted at the center of the bent portion, as at 29, to the center of the lower side of the yoke 20 of the rocker arm or lever IS. The outer end of the rocker arm or lever 24, is provided with a pin 25 that is slidably engaged in the slot 28 to permit of relative movements between the arms or levers as required.

I -or lug 32 which engages. in a slot I6 in the hub posed.

of the drum 16, when the key is normally dis- The key 30 extends forwardly'within the slot l2 to a point beyond the outer rocker arm or lever 26, where it is enlarged to the form of an isosceles triangle, as at 33, that has the vertex portions of its longer side projecting from opposite sides of the shaft I2. The rocker arm or lever 24 is tobe connected to the shaft 12 when the drum IE is disconnected therefrom, and to this end the key 30 is provided with a second offset or lug 34 which is projected from the slot l2 and into engagement with a slot 24' in the hub of the rocker arm or lever 24, whenever the key 30 is actuated to withdraw the offset or lug 32 from the slot l6 of the drum [6. To actuate the key 30, to disconnect the drum 16 from the shaft l2 and to simultaneously connect the rocker arm or lever 24 thereto, an actuator or switching device, in the form of a secnd and smaller drum 35; is rotatably mounted on the front end of the shaft l2 and has a cam element 36 on its inner side for cooperation with the opposed end of the key, whenever the drum 35 is rotated by a cable 39 leading to the bandspread control (not shown) on the control panel of the radio receiver. Extending radially from the inner side of the drum 35 is an arm 3'! that carries a pin 38 at its outer end for engagement in the slot 28 of the rocker arm or lever 26, inwardly from the engaged position ofthe pin on the rocker arm or lever 24. Thus, with the dial ,drum l6 disconnected from the shaft l2, its

rotative motion is transmitted to the shaft l2 through the cam and rockerarm or lever mechanism in a greatly reduced ratio in relative turning movements, but which ratio may be varied through a settingof the pin 38 on the radial arm 31 of the key actuator drum 35.

In the operation of the tuning control thus provided, and for regular signalreception tuning, the dial drum [6 will be connected to the t shaft l2 by the key being normally disposed so that the offset or lug 32 is engaged in the slot I6 in the hub of the drum IS, in which position of the key, the ofiset or lug 34 will be disengaged from the slot 24 of the rocker arm or lever 24. With this setting, the station selector dial of the radio receiver can be manipulated over the entire broadcast band and its motion will be transmitted to the rotor of the-tuning condenserA by the cable I1, thesdrum l6 and the shaft l2, the rotative motion being substantially one hundred and eighty degrees.

Now, to change over to band-spread tuning;

the actuator drum 35 will be rotated by the cable 39 from a band-spread control (not shown), on the control panel of the radioreceiver, to move the cam element 36 into engagement with the opposed end of the key 30, when the latter will be rocked on its pivot 3l' to withdraw the offset or lug 32 from the slot IBof the dial drum l6 and, at the same time, move the offset or lug into engagement with the slot 24' of the rocker arm or lever 24. With this position of the'parts,

the drum I6 is disconnected from the shaft l2- and its rotative motion is to be transmitted to the shaft l2, and the rotor of the condenser A, through the rocker arm or lever mechanism. Upon manipulation of the cable I], from the station selector dial, the motion of the eccentric the rocker arms or levers 24 and 26 can be varied by the setting of the pin 38 relatively to the slot 28 which is effected from the actuator drum 35 that has a maximum range of movement to adjust the pin 38 for rotative motion through an arc slightly greater than one hundred and eighty degrees. In any case, the amount of bandspread to be obtained will depend upon the dimensions of the inter-related parts of the mechanism.

Having thus fully described my invention, it istc be understood that various changes in form and minor details of construction may be resorted to, without departing from the spirit of the invention, or its scope as claimed.

What I claim is:

1. In combination, a tuning condenser for radio receivers and a control mechanism therefor, said mechanism comprising a shaft adapted to be connected to the rotor of the condenser a drum on said shaft, a cable on said shaft a cable connecting said drum with means for rotating said drum for efi'ecting its normal low reduction operation for rough tuning, an eccentric cam element mounted on the front side of said drum, a. yoke engaging said cam; said yoke having formed at the lower end of a rocker arm which is pivotally mounted for cooperative relation with respect to said cam, a second rocker arm pivotally mounted on said eccentric, and a third rocker arm Pivotally mounted on said second rocker arm and control means is disconnected from said rotor,

Val

and means for disconnecting the first named con;-

trol means from the condenser rotor and si-' multaneously connecting said eccentric thereto.

2. 'I'he'combination as in claim 1, with the saidmechanism adapted to be mounted on the chassisd of a radio receiver and having means for sup-' porting the shaft and coupling it to the rotor of' the tuning condenser. if a 3. A mechanical control mechanism forth tuning systems of radio receivers, comprising means adapted to be connected to the rotor of the tuning condenser of a radio receiver for effecting its normal low reduction operation for rough tuning, an eccentric adapted to be connected to the condenser rotor and a. plurality'of rocker arms coacting with said eccentric for effecting its high reduction operation for fine tuning, and means for disconnecting the first named means from the condenser rotor and simultaneously connecting said eccentric thereto.

4. The mechanism as in claim 3, with the first named means and saideccentric in unit assembly with a shaft adapted to be coupled to the rotor of the condenser. I

5. The mechanism as in claim 3, with the first named means having the form of a rotatable drum adapted to be actuatedfrom the station selector dial of the radio receiver by a cable connecting said drum and said dial and the said eccentric and said rocker arms adapted to be actuated from the drum.

6. A mechanical control mechanism for. the tuning system of a radio receiver, comprising a shaft in connection with the rotor of the tuning condenser of the receiver, a drum rotatably mounted on said shaft and adapted to be actuated J from the signal selector dial f the receiver by a, cable connecting said drum and said dial for effecting the normal low reduction operation of the condenser for rough tuning, a system of levers adapted to be connected to the shaft by means of an eccentric mounted on aid drum, said eccentric adapted to actuate said system of levers for eifecting a high reduction operation of the condenser for fine tuning, and means for disconnecting said drum from said shaft and s1- multaneously connecting one of the levers 01' said system thereto.

7. The mechanism as in claim 6, with the said eccentric taking the form of a cam element.

' 8. The mechanism as in claim 6, with said means taking the form of a key that is pivotal! mounted in a slot in said shaft and a dial con trol for actuating the key.

CHARLES F. MATHEWSON. 

